55 degrees is pretty cold for spraying auto finishes but that would normally result in sags, runs, very long flash time. What was the temperature of the metal? did you have a lot of air movement? It appears that you have too high air volume/too little liquid, or the gun is too far from the panel or moving too fast across the panel. I would cut the mix with the fast reducer due to low ambient temperature and practice on some disposable surface. The PPG epoxy primer that I have used lays very smooth and needs zero sanding, I use a conventional siphon gun at lower pressure than recommended or an airbrush.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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